Various display devices have, in the past, been proposed for providing an observer with an image which changes in dependence on the relative position of the observer and the display device. For example, U.S. Pat. No. 3,241,429, issued Mar. 22, 1966 to H. D. Rice et al., relates to a pictorial parallax panoramagram unit which comprises a lineated image layer and a lenticular screen fixed directly over the lineated image layer. The lenticular screen comprises a series of semi-cylindrical or partially cylindrical curves forming the forward faces of elongate lens elements which have planar rear faces. On the image layer, and corresponding to each of the lens elements, there are provided two different panels which, in combination, form two separate images, which are successive images of a scene so as to provide the impression of movement when the display panel is viewed from different angles. Since this display device is of a generally planar shape, there is no suggestion of effecting relative rotation of the display device and the observer in such a manner as to be able to present, for example, a cyclically varying sequence of images nor is there any suggestion that the device may be viewed from any location about the device.
In U.S. Pat. No. 3,586,592, issued June 22, 1971 to L. Cahn, there are described various display devices intended to provide a three dimensional picture by enabling the viewer to simultaneously view different picture elements, but again there is no suggestion of a relatively rotatable arrangement of the display device and the observer.
Other display devices are disclosed in U.S. Pat. Nos. 2,514,814, issued July 11, 1950 to G. Towne; 3,686,781, issued Aug. 21, 1972 to Hugh C. Calhoun, Jr.; 3,538,632, issued Nov. 10, 1970 to K. Anderson and 4,034,495, issued July 12, 1977 to Jerome H. Lemelson.